I just ordered a new external hard drive. This is my third since I bought a digital SLR. I've filled 100 Gigs of storage since I bought my EOS 1D, about two years ago. Yesterday I order a 160 Gig USB 2.0 external drive for $165 from B&H. $1 a Gig. Storage is getting cheap! And internal drives cost less than half as much.
Anyway, be warned. Commiting to digital photography means storage issues. It's cheaper than film and processing. But there are still costs and planning involved.